Details

Autor(en) / Beteiligte

• Poddar, Madhurima
• Jang, Youngwoo
• Misra, Rajneesh
• D'Souza, Francis

Titel

Excited‐State Electron Transfer in 1,1,4,4‐Tetracyanobuta‐1,3‐diene (TCBD)‐ and Cyclohexa‐2,5‐diene‐1,4‐diylidene‐Expanded TCBD‐Substituted BODIPY‐Phenothiazine Donor–Acceptor Conjugates

Ist Teil von

• Chemistry : a European journal, 2020-05, Vol.26 (30), p.6869-6878

Ort / Verlag

Germany: Wiley Subscription Services, Inc

Erscheinungsjahr

2020

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• A new set of donor–acceptor (D–A) conjugates capable of undergoing ultrafast electron transfer were synthesized using 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY)‐substituted phenothiazine, SM1–SM3, by a Pd‐catalyzed Sonogashira cross‐coupling reaction and a [2+2] cycloaddition–electrocyclic ring‐opening reaction. The incorporation of 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) and cyclohexa‐2,5‐diene‐1,4‐diylidene‐expanded TCBD (abbreviated as DCNQ=dicyanodiquinodimethane) in BODIPY‐substituted phenothiazine resulted in significant perturbation of the optical and electronic properties. The absorption spectrum of both SM2 and SM3 showed red shifted absorption as compared to SM1. Additionally, both SM2 and SM3 exhibited a distinct intramolecular charge‐transfer (ICT) transition in the near‐IR region more so for SM3. The electrochemical study revealed multi‐redox processes due to the presence of redox‐active phenothiazine, BODIPY, TCBD or DCNQ entities. Using data from spectral, electrochemical and computational studies, an energy‐level diagram was established to witness excited‐state electron‐transfer events. Finally, evidence of electron transfer and their kinetic information was secured from studies involving a femtosecond transient absorption technique. The time constants for excited‐state electron‐transfer events in the case of SM2 and SM3 were less than 5 ps revealing ultrafast processes. Charge‐transfer interactions: Supramolecular triads featuring centrally positioned dicyanoquinodimethane or tetracyanobutadiene electron acceptors, in a phenothiazine‐BODIPY conjugate, are shown to reveal ground‐state charge‐transfer interactions leading to electron‐transfer products upon photoexcitation (see figure).